Stool



FIG. 1 is a front view of my new design relating to a stool;

FIG. 2 is a rear view of my new design;

FIG. 3 is a right-side view of my new design, the left-side view being symmetric and specular with respect to the right-side view;

FIG. 4 is a top plan view of my new design; and,

FIG. 5 is a bottom plan view of my new design. 

The ornamental design for a stool, substantially as shown and described. 